Question

tính tổng

4/1.3  + 6 / 3.6 + 8/6.10+14/10.17+ 12/17.23

bạn nào trả lời nhanh mình tick cho nha

Answer 1

Đặt A =4/1x3 + 6/3x6+8/6x10 +14/10x17 +12/17x23 . => A/2 = 2/1x3 +3/3x6 +4/6x10+7/10x17 +6/17x23. =>A/2 = 1-1/3 + 1/3-1/6+1/6-1/10+1/10-1/17+1/17-1/23. => A/2=1-1/23 . => A/2=22/23 . => A=44/23 . cho mik nha

​

​

​

​

​

​

​

Answer 2

\(A=\frac{4}{1.3}+\frac{6}{3.6}+\frac{8}{6.10}+\frac{14}{10.17}+\frac{12}{17.23}\)

\(=2\left(\frac{2}{1.3}+\frac{3}{3.6}+\frac{4}{6.10}+\frac{7}{10.17}+\frac{6}{17.23}\right)\)

\(=2\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+\frac{1}{10}-\frac{1}{17}+\frac{1}{17}-\frac{1}{23}\right)\)

\(=2\left(1-\frac{1}{23}\right)\)

\(=2\cdot\frac{22}{23}=\frac{44}{23}\)